1990 200 HP Black Max dies beyond idle

Hi All,

History... Pick up this Chris-Craft Scorpion with a 1990 200 hp Black Max a couple months ago. Rebuilt all cabs, rebuilt fuel pump, changed fuel lines from tank to carbs, changed plugs, and replaced fuel water separator. Tank was empty when i got it so no junk in there. Took the boat out 4 times over the course of July so far and has ran great no issues. Saturday night was going to head out again and the motor would die... ie. fell flat on its face beyond idle. In fact, before i rebuilt the cabs and fuel pump it had the exact same symptom. It was then hard to start after that, once started i tried to get going again and it sounded like it wanted to go but once i hit 1500 rpms it died... i tried squeezing the bulb but its hard as a rock and trying to pump it did not change how motor behaved. Is it possible my fuel pump died again? I plan on looking at it after work tonight and cannot help but notice this is the same way she ran with carbs full of junk and a bad fuel pump.

Also... Boat has 2 new batteries... one starting ... and a house battery... + oil injection had been bypassed by previous owner... running pre-mix 50:1.

Thanks,

Eric

Re: 1990 200 HP Black Max dies beyond idle

Eric, It sounds like incorrect idle mixtures or dirty carbs. Sorry. If fuel pump was bad, fuel primer would likely fill crankcase with raw fuel.

Re: 1990 200 HP Black Max dies beyond idle

Thanks Chris... I have a bit more information as i just left the boat yard. I had a two part problem.

1) Clamp holding fuel feed line to fuel pump was loose allowing air to enter system... fixed
2) Port side of motor is not getting spark... the problem


Since i doubt i have three bad coils, wires, and plugs it must be a switch box or stater? Looking at the small wires on the starboard side of the motor the insulation is failing leaving the wire ends exposed slightly. The wires are still making continuity as confirmed with multi-meter. Not sure if this is contributing to the problem or not, i just noticed it.

I pulled all six plugs while i was in there and they looked really good.

What does this sound like? (no jokes on how a v6 sounds like running on 3 cylinders... its fresh in my mind )


Thanks,

Eric

Re: 1990 200 HP Black Max dies beyond idle

Switch box most likely...Buy Mallory and don't pay Merc pricing....replace both of them or have problems down the road..They are around $115 per and you need two...I would do some more testing before running out and buying..Buy the way Merc boxes are around $200 or so depending where you get them...The Mallory are made in Germany!!!! however welcome to the older merc's and the insulation problem...taping is not the answer..need to replace or splice the wires..you can buy new harness from CDI.......

Re: 1990 200 HP Black Max dies beyond idle

Thanks for the info... The wires going to that switch box do not look so well.. hoping maybe one is rotted somewhere and that's the problem. Last time out we rode through some slope for about an hour, wondering if that didn't help.

I will test this out tonight...

Thanks,

Eric

Re: 1990 200 HP Black Max dies beyond idle

Update 07/31/13 - went to boat storage yard and looked closely at wiring going to switch boxes. They were all connected and just the ends have a insulation problem. Looks like one switch box was replaced (outer) as it "looks" newer than the other, plus the Phillips head screws are all buggered up. To test it wasn't the stater i swapped the wires around between switch boxes for the stater. The result was the same, no spark on the port side of the motor. Other than swapping switch boxes around what other tests can be done to isolate this as a switch box problem? (I was going to switch them around tonight but the children were getting restless )

Thanks,

Eric

Re: 1990 200 HP Black Max dies beyond idle

Update 08/12. Saturday replaced both switch box's and spliced in/soldered new wiring to switch boxes. Motor fired up on the first shot and was idling around 1400 rpms on the hose! Lowered idle to around 900 and buttoned her up... Took her out fishing offshore yesterday and it ran like a champ!!! Thanks for the help... The motor sounded far better then it ever did before, no hiccups and power was instant... I even picked up around 500 rpms.... previous max rpm with normal load was about 5200.. I hit 5700 rpms yesterday blasting through a light chop with a half tank of gas, two adults, two children, and the normal stuff that comes with everyone.


Thanks again... we had a awesome day fishing yesterday!!!


Eric